ansys.net search results
quick file search:
    home » search results
 
 
Structural Nonlinearities Tips (42 entries)
 
22x Coupled-Field Elements [PDF]
  Sheldon Imaoka (ANSYS, Inc.)
  "The 22x direct coupled-field elements (PLANE223, SOLID226-227) provide a wide array of material behavior for multiphysics applications - these include piezoelectricity, piezoresistivity, thermoelasticity, and thermoelectricity. This memo hopes to introduce some of the pertinent features of these elements."
(Week 34, week of 06/11/06.)
[permalink]
 
Average Rating: 8.9 (37 votes)  
Rate this item:
 
Analyzing Hyperelastic Materials w/ Some Practical Considerations
  Paris Altidis and Vince Adams
  Presentation from the Midwest ANSYS User Group
[ANSYS Nonlinear, version unspecified]
[permalink]
 
Average Rating: 10.0 (8 votes)  
Rate this item:
 
Beta Electrical Contact Features at 6.0 [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "This issue describes a beta feature at 6.0, which is electrical contact capability of 17x surface-to-surface contact elements. This new capability allows contact in thermal-electric and structural-thermal-electric problems."
(Week 13, week of 01/07/02.)
[permalink]
 
Average Rating: 7.9 (28 votes)  
Rate this item:
 
BOOT
  Sheldon Imaoka (ANSYS, Inc.)
  Old model originally created back in ANSYS 6.0. Recently tested and seems to solve fine as-is in ANSYS 12.1, so I expect all versions in-between should run fine, too. Hyperelasticity, self-contact, rigid-deformable contact are present. Animation of same model (with finer mesh) is on the gallery page.
[permalink]
 
Average Rating: 8.3 (3 votes)  
Rate this item:
 
Buckling in Workbench Simulation [PDF]
  Sheldon Imaoka (ANSYS, Inc.)
  "Buckling may be a concern for some situations, where a user may need to modify the design to prevent buckling within a given load range. Conversely, failure analysis may need to be performed when a structure has collapsed.
ANSYS and Workbench Simulation have many tools to aid users in solving geometric instability problems, ranging from linear (eigenvalue) buckling to nonlinear, post-buckling analyses."

(Week 41, week of 10/14/07)
[permalink]
 
Average Rating: 8.9 (63 votes)  
Rate this item:
 
CERIG vs RBE3, RIGID184 [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "Constraint equations provide many useful features in ANSYS, such as tying together dissimilar meshes, representing parts of the system not explicitly modeled, or distributing loads. Two automated methods of generating constraint equations are the CERIG and RBE3 commands. Because there is often confusion over their use, this memo hopes to provide some information on differences between the two methods.
"Constraint equations in ANSYS are linear, so they are not valid for large-rotation analyses. RIGID184 is a beta element in version 6.1 which provides rigid link/beam capabilities, valid for large-rotation problems. The latter part of this memo will cover some details of this undocumented feature, available in 6.1."

(Week 19, week of 07/08/02.)
[permalink]
 
Average Rating: 9.9 (69 votes)  
Rate this item:
 
Chaboche Nonlinear Kinematic Hardening Model [PDF]
  Sheldon Imaoka (ANSYS, Inc.)
  "The Chaboche nonlinear kinematic hardening model was added in ANSYS 5.6 to complement the existing isotropic and kinematic hardening rules that users relied on. Despite its availability for nearly ten years as of the time of this writing, the Chaboche model has enjoyed limited popularity, in part because of the perceived complexity of calibrating the material parameters. This memo hopes to introduce the basics related to the Chaboche nonlinear kinematic model."
(Week 47, week of 05/04/08)
[permalink]
 
Average Rating: 9.6 (14 votes)  
Rate this item:
 
Contact Analysis Tips [PDF]
  Sheldon Imaoka (ANSYS, Inc.)
  "Generally speaking, nonlinear analyses involving contact can be quite challenging to solve when the contacting area changes during the load history. However, ANSYS Workbench Simulation has very robust contact technology, along with diagnostic tools that can help the user obtain converged, accurate solutions. This memo hopes to discuss some tips related to contact analyses in hopes of aiding the user who encounters difficulties when solving contact analyses."
(Week 52, week of 02/22/09)
[permalink]
 
Average Rating: 9.7 (29 votes)  
Rate this item:
 
Contact Wizard Enhancements at 6.0 [PDF]
  Sheldon Imaoka (ANSYS, Inc.)
  Describes some of the enhancements made to the Contact Wizard at ANSYS 6.0, including support of 17x contact elements' thermal features and ability to edit contact pair options through same interface.
(Week 5, week of 10/22/01.)
[permalink]
 
Average Rating: 9.3 (23 votes)  
Rate this item:
 
Converting Prony Series to Frequency Domain
  Sheldon Imaoka (ANSYS, Inc.)
  Simple example showing how to convert Prony series for viscoelasticity from time domain to frequency domain. This is to convert TB,PRONY to TB,ELASTIC/SDAMP for use in harmonic response analyses.
[permalink]
 
Average Rating: 10.0 (7 votes)  
Rate this item:
 
Creep and Plasticity
  Guoyu Lin (ANSYS, Inc.)
  Discussion on creep (implicit and explicit time integration), along with using it with plasticity models. (From XANSYS posting)
[permalink]
 
Average Rating: 9.9 (37 votes)  
Rate this item:
 
Difference between Large rotation, Finite Strain, Stress-Stiffening
  Sheldon Imaoka (CSI)
  Discussion on the differences between large rotation (large deflection), finite strain (large strain), and stress-stiffening effects in nonlinear analyses. (From XANSYS posting)
[permalink]
 
Average Rating: 9.6 (13 votes)  
Rate this item:
 
Difference between PSTRES and SSTIF
  Sheldon Imaoka (CSI)
  Discussion on the differences between PSTRES and SSTIF commands. (From XANSYS posting)
[permalink]
 
Average Rating: 10.0 (10 votes)  
Rate this item:
 
Differences Between Implicit and Explicit Dynamics
  Sheldon Imaoka (ANSYS, Inc.)
  Discussion of the differences between implicit and explicit dynamics. (Differences between regular ANSYS and ANSYS/LS-DYNA)
[permalink]
 
Average Rating: 8.1 (39 votes)  
Rate this item:
 
Drucker-Prager Models [PDF]
  Sheldon Imaoka (ANSYS, Inc.)
  "The Drucker-Prager material model is used for pressure-dependent inelastic behavior of materials such as soils, rock, concrete, and powder. Because ANSYS offers three different Drucker-Prager constitutive models, this memo hopes to provide a comparison of the available options."
(Week 44, week of 03/16/08)
[permalink]
 
Average Rating: 9.8 (24 votes)  
Rate this item:
 
Hill's Potential [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "Anisotropic plasticity using Hill’s yield criterion was introduced in ANSYS 5.7, and the extensions to anisotropic creep and viscoplasticity were added in ANSYS 6.0. While Hill’s stress potential is most commonly used for rolled sheets, it can be used for other situations where three orthogonal planes of symmetry are preserved. This memo will introduce details of the usage of Hill’s potential in ANSYS."
(Week 50, week of 08/31/08)
[permalink]
 
Average Rating: 10.0 (4 votes)  
Rate this item:
 
Load vs. displacement control in contact problems [PDF]
  Karen Dhuyvetter (CSI)
  Discussion on load vs. displacement control for contact problems.
[permalink]
 
Average Rating: 10.0 (18 votes)  
Rate this item:
 
Manual Calculation of Strain Energy Density [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "Output of elastic, plastic, and creep strain energy densities (SEND) was introduced in ANSYS 6.0, although this is limited to 18x elements in nonlinear analyses. Users whose models include core elements with plasticity and creep may also wish to obtain these quantities, and this memo hopes to review this procedure."
(Week 22, week of 12/22/02.)
[permalink]
 
Average Rating: 10.0 (19 votes)  
Rate this item:
 
Modeling preloaded bolts [PDF]
  Sheldon Imaoka (CSI)
  Modeling preload in bolts via contact offset, thermal contraction, or the new pretension elements PRETS179.
PRELOAD1, PRELOAD2, and PRELOAD3 input files
[permalink]
 
Average Rating: 10.0 (12 votes)  
Rate this item:
 
Modeling Viscous Behavior [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "Amorphous solids or solids at elevated temperatures may exhibit viscous behavior. It may be difficult for some users to determine how best to model such behavior. This memo hopes to describe some available options in ANSYS and to differentiate between viscoelastic and viscoplastic constitutive models."
(Week 36, week of 12/03/06.)
[permalink]
 
Average Rating: 10.0 (10 votes)  
Rate this item:
 
Multiframe Restarts [PDF]
  Sean Harvey (CSI)
  Memo covering the multiframe restart capability (RESCON) in ANSYS.
Accompanying input file
[permalink]
 
Average Rating: 4.5 (10 votes)  
Rate this item:
 
Nonlinear monitoring [PDF]
  Sheldon Imaoka (CSI)
  Memo covering the benefits of the jobname.mntr file and the MONITOR command in nonlinear analyses.
[permalink]
 
Average Rating: 10.0 (9 votes)  
Rate this item:
 
Nonlinear Submodeling [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "Submodeling is often used to efficiently obtain solutions at local areas. Although submodeling may be commonly thought of as being applicable to linear static structural solutions, it can also be applied to nonlinear and transient analyses, as well as other disciplines. This memo hopes to cover the specific case of nonlinear static structural submodeling."
(Week 14, week of 01/14/02.)
[permalink]
 
Average Rating: 9.7 (19 votes)  
Rate this item:
 
PDF file summarizing beta contact features at 5.6.1 [PDF]
  Sheldon Imaoka (CSI)
  Presentation on the thermal contact and fluid pressure capabilities of the surface-to-surface contact elements. This was written when these capabilities were beta at 5.6. Thermal capabilites are documented at 5.7.
Accompanying thermal contact example and fluid pressure example
[permalink]
 
Average Rating: 10.0 (5 votes)  
Rate this item:
 
PDS and Nonlinear Runs [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "The Probabilistic Design System (PDS) of ANSYS provides a very powerful tool in understanding the effect of uncertainties in one’s design. The details of PDS are covered in the online help, so this memo will discuss the specific case of setting up serial and parallel PDS runs as well as performing nonlinear analyses with PDS."
(Week 23, week of 03/14/04.)
[permalink]
 
Average Rating: 10.0 (6 votes)  
Rate this item:
 
Plasticity Hardening Rules [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "ANSYS has a wide range of constitutive models and element technology available to the user. In this memo, the basics of isotropic and kinematic hardening for plasticity will be discussed, specifically related to proportional/non-proportional, monotonic/cyclic loading, and finite strain applications."
(Week 11, week of 12/17/01.)
[permalink]
 
Average Rating: 9.3 (23 votes)  
Rate this item:
 
Preventing Rigid-Body Motion in Contact Problems [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "In contact problems run in a static manner, controlling rigid-body motion may sometimes be an issue under the following circumstances: (a) force-controlled systems or (b) multiple bodies with some parts unconstrained."
"This memo hopes to address some ways of controlling rigid-body motion in contact problems through the use of options available with the surface-to-surface contact elements."

(Week 2, week of 10/03/01.)
[permalink]
 
Average Rating: 9.7 (18 votes)  
Rate this item:
 
QR Damped and Unsymmetric Stiffness [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "There have been significant enhancements to the QR Damped eigenvalue extraction method in the past several releases of ANSYS. At 8.0, the capability of including unsymmetric damping [C] matrix was introduced, along with support of damping defined via the DMPRAT and MDAMP commands.
ANSYS 8.1, the material-based constant damping ratio MP,DMPR allowed users to specify constant damping ratios per material ID in mode-superposition harmonic analyses, when used with the QRDAMP eigensolver. With the release of 9.0, QRDAMP also supports unsymmetric stiffness [K] matrix, output of complex eigenvectors, and the use of the PSOLVE command. This memo hopes to cover the use of QR Damped eigenvalue extraction method in friction problems, where an unsymmetric stiffness [K] matrix may be present. An example of this type of problem is brake squeal analyses, where the combination of ANSYS 17x contact elements and the QRDAMP eigensolver provide an easy-to-use, efficient means of determining unstable modes."

(Week 29, week of 01/09/05.)
[permalink]
 
Average Rating: 9.4 (16 votes)  
Rate this item:
 
Review of Anisotropy, Yield Criteria, Failure Criteria [PDF]
  Sheldon Imaoka (ANSYS, Inc.)
  "This memo hopes to serve as a review of the basics of anisotropy, yield criteria, failure criteria, and the ANSYS procedure related to these topics."
(Week 15, week of 01/21/02.)
[permalink]
 
Average Rating: 8.8 (20 votes)  
Rate this item:
 
Shape Memory Alloy
  Sheldon Imaoka (ANSYS, Inc.)
  Short PDF describing differences between the superelastic and shape memory effect options for Shape Memory Alloy (SMA) material model. Simple input file can be downloaded here.
[permalink]
 
Average Rating: 9.5 (11 votes)  
Rate this item:
 
SIYSDCAP
  Sheldon Imaoka (ANSYS, Inc.)
  Tip on visualizing the Drucker-Prager Cap model yield surface.
[permalink]
 
Average Rating: 8.4 (16 votes)  
Rate this item:
 
Stress vs Strain Experimental Curve
  Guoyu Lin (ANSYS, Inc.)
  Discussion on stress vs. strain curves, plasticity, element formulation, necking, and undocumented NLISO option.
[permalink]
 
Average Rating: 9.4 (9 votes)  
Rate this item:
 
Techniques for Successfully Using ANSYS Contact Elements
  Rich Bothmann
  Presentation from the Midwest ANSYS User Group
[ANSYS Nonlinear, version 9.0]
[permalink]
 
Average Rating: 9.4 (9 votes)  
Rate this item:
 
Thermal contact overview [PDF]
  Yongyi Zhu (ANSYS, Inc.)
  Presentation on the thermal contact capabilities of the surface-to-surface contact elements, beta at 5.6.
Input file for pressure-dependent thermal conductance

[permalink]
 
Average Rating: 9.7 (17 votes)  
Rate this item:
 
Understanding Lagrange Multipliers [PDF]
  Sheldon Imaoka (ANSYS, Inc.)
  "Lagrange multipliers are a general term used in different areas of ANSYS, specifically contact and element formulation. This memo hopes to provide the user with a simplified introduction to the most important concepts in using elements with Lagrange multipliers, in hopes that some of the element options and solver selection can be better understood.
Currently, at ANSYS 6.0, the node-to-node gap element CONTA178 and the Mixed U-P formulation of the 18x elements (i.e., KEYOPT(6)>0) utilize Lagrange multipliers, so the discussion will focus on these elements."

(Week 7, week of 11/05/01.)
[permalink]
 
Average Rating: 8.4 (16 votes)  
Rate this item:
 
Undocumented Hyperelastic Material Models at 5.7-6.1 [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "From 5.7, the 18x series of elements support a variety of hyperelastic constitutive models, namely general polynomial, Mooney-Rivlin, Neo-Hookean, Arruda-Boyce, and Ogden. Four other models have been included in 5.7 onwards, although these are undocumented options for TB,HYPER. These four models consist of the Yeoh and Gent models for incompressible behavior and the Hyperfoam and Blatz-Ko options for compressible rubbers. This memo hopes to provide a summary of these material models and of the required input."
(Week 18, week of 03/11/02.)
[permalink]
 
Average Rating: 8.0 (20 votes)  
Rate this item:
 
User-Defined Creep Laws with USERCREEP [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "ANSYS provides 13 creep equations for use with implicit creep – these range from the simple Norton law to the hyperbolic sine form to the Blackburn model to a rational polynomial expression, to name a few – that can be used to model a range of creep behavior for metals. The TBFT command provides curve-fitting functionality for the user wishing to evaluate creep material parameters from test data. Also, the user can model anisotropic creep as well as combine implicit creep with rate-independent plasticity to model a wide range of complex material response.
Despite this wealth of features, however, one may wish to incorporate one’s own creep law into ANSYS. For example, a company may have their own creep equation with material parameters already defined and validated through testing. The built-in creep laws in ANSYS assume creep used in design rather than failure analysis, so the available creep laws are meant to model primary and secondary creep – consequently, another need to incorporate a user-defined creep law would arise when a user wants to include tertiary creep and/or to evaluate creep damage.
This memo will hope to address some aspects of writing one’s own user-defined creep law with the USERCREEP.F subroutine to address this issue."

Example using Anand's model.
(Week 40, week of 10/07/07)
[permalink]
 
Average Rating: 9.7 (15 votes)  
Rate this item:
 
User-Defined Hyperelasticity with USERHYPER [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "User-Programmable Features (UPFs) are an extremely useful feature for analysts that need additional advanced functionality, especially in the area of constitutive modeling.
TB,HYPER allows users to include many incompressible and compressible hyperelastic material behavior – Ogden, Arruda-Boyce, Gent, Yeoh, Blatz-Ko are but some of the available models. However, for those wishing to use a customized strain energy function, the USERHYPER.F subroutine is available."

(Week 39, week of 09/30/07.)
[permalink]
 
Average Rating: 10.0 (4 votes)  
Rate this item:
 
User-Defined Output with USEROUT.F [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "There are various situations where a user may wish to define specific type of output to postprocess — this can range from simple evaluation of safety factors to more involved damage calculations. While APDL, the ANSYS command language, allows users to manipulate results in any manner one sees fit, user-programmable features (UPFs) also provide a means for users to calculate specific output results efficiently at the solution level."
Example of calculating fatigue and Cap (Extended Drucker-Prager) output.
(Week 48, week of 06/01/08)
[permalink]
 
Average Rating: 10.0 (5 votes)  
Rate this item:
 
Using Birth and Death with Multiframe Restart
  Odd Einar Lindøe (Imenco Engineering)
  Tips on using element birth and death (EKILL/EALIVE) with multiframe restart (RESCONTROL). By default, one cannot use birth and death with multiframe restart since the .rdb file is resumed (and the latest information is in .db, not .rdb). This tip shows some methods of using birth and death with multiframe restart.
[permalink]
 
Average Rating: 9.6 (14 votes)  
Rate this item:
 
Using CMS in Workbench Simulation [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "At Workbench 11.0, the ANSYS Rigid Dynamics add-on module enables users to model complex kinematic assemblies, whereby system-level performance as well as accurate force loading on components can be obtained.
Although the parts in the assembly may initially be considered rigid, an interesting, related method is the use of component mode synthesis (CMS) to account for the flexibility of parts. This memo will attempt to cover a way in which users can incorporate CMS in their multibody analyses in Workbench Simulation."

[For version 12.0, use supplied "cms_use_v12.mac" instead of "cms_use.mac" - courtesy of D. Creech.]
(Week 37, week of 05/27/07.)
[permalink]
 
Average Rating: 9.8 (28 votes)  
Rate this item:
 
Viscoelasticity [ZIP]
  Sheldon Imaoka (ANSYS, Inc.)
  "Viscoelastic constitutive models allow users to analyze the time-dependent relaxation or creep behavior of materials, including glass, polymers, solid rocket propellants, to name a few. One may view viscoelastic materials as containing an elastic and viscous component, similar to a spring and dashpot in series. This memo will introduce viscoelastic input in ANSYS and as well as cover curve-fitting procedures."
(Week 49, week of 06/08/08)
[permalink]
 
Average Rating: 9.8 (21 votes)  
Rate this item: